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Introduction
“Man did not weave the web of life; he is merely a strand in it. Whatever
he does to the web, he does to himself.”
—Attributed to “Chief Seattle” (Noah Sealth, 1786-1866)
The public benefits from a wide variety of resources and processes that
are provided by natural ecosystems. Collectively, these benefits are known
as ecosystem services. Ecosystem services are produced as a byproduct of
the functioning of the ecosystem—the interactions of plants, animals, and
microbes with the environment. The benefits provided by ecosystem services
are ubiquitous and immensely valuable to society. They include
• Provisioning services or the material goods provided by ecosystems
(often simplified to food, feed, fuel, and fiber);
• Regulating services (e.g., climate regulation, flood control, water
purification);
• Cultural services (e.g., recreational, spiritual, aesthetic); and
• Supporting services (e.g., nutrient cycling, primary production, soil
formation).
These ecosystem services ultimately underpin the well-being of all people.
When events occur that interrupt or interfere with the normal functioning of
ecosystems, ecosystem services may be impacted, causing both short- and
long-term harm to the ecosystem and those dependent upon it. Under-
standing and quantifying the nature and level of these impacts is a difficult
and complex task, but can be used to establish appropriate procedures
for recovery, restoration, management, and, when applicable, for seeking
compensation for damages.
The Oil Pollution Act of 1990 creates a formal legal framework for
determining when an oil spill results in an “injury” (defined as an observ-
able or measurable adverse change in a natural resource or impairment of
a natural resource service) to the “trust” resources or resource services.1 A
See http://www.epa.gov/oem/content/lawsregs/opaover.htm.
1
17
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18 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
process known as Natural Resource Damage Assessment (NRDA) is used by
“trustees” to determine the extent and severity of that injury. Trustees, who
include representatives of the federal government, tribes, and affected state
governments, must attempt to (1) quantify the extent of damage; (2) develop,
implement, and monitor restoration plans; and (3) seek compensation for
the costs of assessment and restoration from those deemed responsible for
the injury. The goal of this effort is to “make the environment and the public
whole for the injuries to natural resources and services” (NOAA, 1996).
Under common NRDA practice, losses are generally measured in eco-
logical terms (e.g., number of acres damaged or number of fish killed)
and restoration generally follows relatively straightforward equivalency ap-
proaches (e.g., acres of habitat restored or fish stocks replaced) (described
in Chapter 2). The injuries to the ecosystem and the services it provides are
quantified by comparing the services to a baseline when possible. When the
service is well known (e.g., the income lost from the closure of a particular
fishery), the assessment of injuries can be straightforward. However, for other
services, their connection to ecosystem condition is less well established
because baseline data have not been collected (e.g., hydrocarbon levels
in marsh sediments) or baseline ecological data have not been linked to
services (e.g., acreage of wetlands but not the value to fisheries).
Additional challenges to assessment arise as the spatial and temporal
scale of the injured system, and the complexity of the ecosystem, increase.
In these cases it becomes increasingly difficult to understand and account
for the full range of ecological impacts and to translate those impacts into
reductions of ecosystem services. It also becomes more difficult to determine
what the baseline conditions might have been in ecosystems subject to other
natural and manmade environmental changes unrelated to a specific event.
The Gulf of Mexico (GoM), often referred to as the Gulf of Mexico Large
Marine Ecosystem (GoM LME), is remarkably rich and complex and provides
a wealth of ecosystem services. The Gulf of Mexico provides important
regulating, supporting, and cultural services, which include coastal tourism
with an estimated worth of $19.7 billion per year (National Commission
on the BP Deepwater Horizon Oil Spill and Offshore Drilling, 2011), storm
surge protection by coastal wetlands, habitat for migrating waterfowl, cy-
cling of nutrients from river discharges, and the unique cultural heritage of
coastal communities. Provisioning services include food, biochemical and
medicinal compounds, clean water, and energy in the form of crude oil and
natural gas. In 2008, the GoM commercial fish and shellfish harvest yielded
a dockside value of $659 million (1.27 billion pounds; NMFS, 2010). These
commercial landings accounted for approximately 25 percent of the seafood
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19
INTRODUCTION
provided by the contiguous United States. The GoM also has significant
recreational fisheries in which 3.2 million citizens participated in 2008; 92
percent were coastal county residents (NMFS, 2010). Sponges, tunicates,
bryozoans, and other invertebrates of offshore hard banks also contribute
provisioning ecosystem services such as pharmacological extracts used for
treatment of cancer, cardiovascular disease, infections, and inflammation.
The long-term development and maintenance of oil and gas extraction
infrastructure has generated a wealth of hydrocarbon resources from the
GoM. In 2009, this extensive infrastructure generated offshore production
of 29 percent of the total crude oil and 12 percent of the natural gas in the
United States2; annual oil production in the GoM exceeded 1.6 million
barrels of oil per day).3 However, this industry has also resulted in altered
coastal zones and changed physical aspects of the coastline that may affect
ecosystem services (Boesch and Rabalais, 1987), constructing numerous
structures on the continental shelf and approximately 25,000 miles of active
oil and gas pipeline on the GoM seafloor. Other pipeline corridors cross
coastal wetlands. Inevitably, minor spills and leaks are associated with large-
scale hydrocarbon production and shipping activities, but historically the
GoM had been spared from a major industry-related accident.
That historical trend ended on April 20, 2010, when the Deepwater
Horizon platform drilling the Macondo well in Mississippi Canyon Block
252 (DWH) exploded, killing 11 oil workers and injuring 17. This event,
which resulted in nearly 5 million barrels (>200 million gallons) of crude oil
released into the GoM over a period of three months, represents an industrial
oil spill of unprecedented magnitude.4 The depth of the release (~1,500
m) and the potential impact this may have on poorly understood deep-sea
ecosystems is also unprecedented. The combination of large commercial
(such as menhaden, blue crabs, oysters, and brown, white, and pink shrimp)
and recreational fisheries (such as red snapper, sea trout, and red drum), a
vibrant tourism industry, and long-established oil production facilities makes
the GoM the most economically productive body of water in North America.
The spill had an immediate impact on this productivity. In the short term, up
to 80,000 square miles of the U.S. Exclusive Economic Zone were closed
to fishing, resulting in loss of food, jobs, and recreation. Similarly, coastal
tourism, beach-going, boating, and other services were heavily affected.
The long-term impacts on these as well as other regulating and supporting
See http://www.eia.gov/special/gulf_of_mexico/index.cfm.
2
See http://www.epa.gov/oem/content/lawsregs/opaover.htm.
3
See http://www.nytimes.com/2010/08/03/us/03flow.html.
4
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20 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
services are much more difficult to discern. They may be considerable, and
may be expressed over years to decades.
Of particular concern was the introduction of oil and dispersants from
the DWH spill at approximately 1,500 m depth directly into a realm of
poorly understood but abundant marine life that includes bottom-dwelling
fish, deep sea corals, and chemosynthetic microbial communities. As oil
and dispersants traveled through the water column, they interacted with
microorganisms, zooplankton, pelagic fish, sea turtles, marine mammals,
and eventually, as they entered the photic zone, marine plankton, fish and
shrimp larvae, and floating eggs in the water column (e.g., bluefin tuna
eggs). Some of the mixture made it to the surface onto beaches, and into
salt marshes, mangroves, or mudflats; potentially impacting the ecosystems
that support important fisheries productivity. Throughout the process, marine
and terrestrial birds, reptiles, and other animals may have been exposed to
chemically dispersed oil and dispersants (National Commission on the BP
Deepwater Horizon Oil Spill and Offshore Drilling, 2011). To completely
understand and quantify the impact of the oil spill thus requires a thorough
understanding of the complex interactions and linkages between and among
the various components and processes of these ecosystems (Figure I.1).
Complicating an understanding of the impact of the DWH spill is the fact
that the GoM is an ecosystem that has been subjected to multiple sources of
stress, both natural and manmade, to its ecological services. In addition to the
long-term impacts of the oil and gas industry, there has been tremendous loss
of coastal wetlands due to multiple interacting natural and human-caused
changes in the geology, hydrology, and landscape. Louisiana has lost more
than 2,300 square miles of coastal wetlands since initiation of levee-building
in 1927 (National Commission on the BP Deepwater Horizon Oil Spill and
Offshore Drilling, 2011) and the dredging of canals for access to oil platforms
and navigation. Not only does the flood control system affect wetlands, but
it also threatens the very existence of coastal communities that ring the Mis-
sissippi Delta. The natural processes of sedimentation and delta construction
that have formed and evolved the region’s landforms over millennia are no
longer in place. Before construction of the Mississippi River basin flood
control structures, approximately 400 million metric tons of sediment were
delivered annually to the Delta; today it is approximately 145 million met-
ric tons (National Commission on the BP Deepwater Horizon Oil Spill and
Offshore Drilling, 2011). A major component of this loss in sediment load
is from the completion of dams and reservoirs on the Missouri River in the
1950s (Blum and Roberts, 2009). Each year nutrients from fertilizers used
in Midwestern agriculture are carried down the Mississippi and Atchafalaya
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21
INTRODUCTION
FIGURE I.1 Schematic drawing indicating various components and processes of the GoM ecosystem. A solid
understanding of the complex interactions among these components is a key aspect of understanding the
impact of the DWH spill on ecosystem services in the GoM. SOURCE: Alan Joyner, Red Twine Art & Design.
rivers, creating plankton blooms in the Gulf that result in the partial (hypoxia)
or complete (anoxia) depletion of oxygen, and massive “dead zones” that
can cover thousands of square miles of Gulf seafloor. Thus any analysis of
the impact of the DWH spill on ecosystem services in the GoM must include
consideration that the Gulf has been, and continues to be, affected by non-
spill-related phenomena and that the baselines against which the impact of
the spill must be judged are both spatially and temporally dynamic.
The magnitude and depth of the DWH event, in concert with the com-
plexity of the GoM LME and the difficulties in establishing baseline values,
pose serious challenges to those charged with carrying out the NRDA pro-
cess, which historically has been applied to shallow-water events of much
more limited extent and scale (see Box 2.1 on the North Cape Oil Spill).
Indeed the National Commission on the BP Deepwater Horizon Oil Spill
and Offshore Drilling describes the assessment of natural resource damage
associated with this particular spill as “the largest and most complex that the
government has ever undertaken to assess oil spill impacts” (National Com-
mission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, 2011).
At the time of writing this interim report, numerous studies focused on
trying to understand the impact of the oil spill on the GoM LME are being
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22 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
conducted, including many in support of the NRDA process. Many thousands
of samples have been collected and observations made, and studies will
continue for some time. Analyses are also under way; some of the results are
being published while others are not yet public. It will take many years to
fully analyze the data and some impacts may not become apparent until far
into the future, if at all. Nonetheless, the government is obligated to conduct
a timely NRDA process to address the public’s many concerns. An example
that highlights the complicated nature of understanding the potential DWH
BOX I.1 DOLPHIN STRANDINGS IN THE GULF OF MEXICO:
THE CHALLENGING SEARCH FOR THE CAUSE
From January through April 24, 2011, 192 bottlenose dolphins, Tursiops
truncatus, stranded along GoM’s coast from Florida to the Texas/Louisiana bor-
der at quadruple or more the average number recorded in the same period
annually from 2002 through 2009. Over a third of them were stillborn and
newborn calves. These strandings led to much media attention, public outcry,
and the speculation that they were associated with the DWH spill. Strandings
in 2010 were also higher than average, peaking in spring and early summer,
but with no unusual number of calves.a In the midst of that peak came the
April 20, 2010, DWH oil spill. On February 28, 2011, the strandings were officially
declared an Unusual Mortality Event (NOAA, 2011a), a designation that calls for
intensified data and sample collection, and a rigorous, coordinated study into
the cause. At the same time, the event was included in the NRDA process, which
assesses damages to marine mammals and their habitat attributed to the spill.
A study of this kind begins with the stranding pattern and proceeds to
a comprehensive search for clues to mortality. For example, certain offshore
forms, like sperm whales, Physeter macrocephalus, and pilot whales, Globiceph-
ala spp., come ashore in the tens to hundreds, at roughly the same time and
place, in what are called mass strandings. The underlying cause is thought to
be behavioral; once a critical member or number of the school heads to shore,
the rest follow (Norris and Dohl, 1980). Bottlenose dolphins, however, do not fall
into that category and usually strand alone or as mother-calf pairs. A few come
ashore alive and some die on the beach, but most wash up already dead. Find-
ing so many carcasses, as in the present event, suggests that over time, some
enduring process or condition at sea is making dolphins sick or killing them.
Knowledge of the animal’s life history, its environment, past stranding ac-
counts in the region and elsewhere, and the presence of other suspected condi-
tions help narrow the search from possible to the more probable causes. Might
this event be in any way similar to the 1990 episode along the Gulf coast, where
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23
INTRODUCTION
impacts is the 2010-2011 stranding of an unusual number of dolphins (many
stillborn and newborn calves) along the GoM coast, which spurred a public
outcry and immediate association with the DWH event. As detailed in Box
I.1 however, many possible causes (natural and manmade) could be linked
to the strandings, and only careful study and analysis will determine if the
DWH spill was ultimately responsible.
Recognizing the unique aspects of the DWH spill (magnitude, duration,
depth, and complexity of the ecosystems involved) and the ramifications of
in the first three months of the year, nearly 300 dead bottlenose dolphins were
found on beaches from Florida to Texas? The cause was not established (Kuehl
and Haebler, 1995). Could what is happening be the result of poisoning by a natu-
ral biotoxin produced by harmful algal blooms, like “red tide” or domoic acid from
toxin-producing diatoms and transferred through prey fish? Bottlenose dolphins
in Sarasota Bay, Florida, for instance, are commonly exposed to these toxins (Fire
et al., 2008) and there is growing evidence that correlates exposure with strand-
ing events along the southeastern and northern Gulf coasts (Flewelling et al.,
2005; Fire et al., 2011). Might these strandings be due instead, or in addition to,
an infectious disease, such as the ubiquitous morbilliviruses that wreak havoc in
dolphins and whales (Duignan et al., 1996)? The stranding pattern supports both
possibilities, while not excluding others. Harmful algal blooms can persist for
months, as can an infectious disease that spreads from one dolphin to another.
The high number of fetuses and young raises pointed questions: does illness
cause early termination of pregnancy; are calves more vulnerable; do the mothers
die first, leaving them helpless? Could anthropogenic contaminants play a role,
such as polychlorinated biphenyls that are known to accumulate in dolphins in
the region (Houde et al., 2006) and may reduce their ability to fight disease (Lahvis
et al., 1995)? To determine if and how the DWH spill fits into the picture, the study
will need to search for measurable differences in those dolphins that stranded
before the spill versus after it (Geraci, 1990).
A probe of this depth and scale, on an event of this importance, will yield
sufficient information that should shed light on the problem. The challenge, as
usual, will be to tease out the cause and account for the roles of other influencing
or confounding biological and environmental factors, including the DWH spill.
See running tally: www.nmfs.noaa.gov/pr/health/mmume/cetacean_gulfofmexico2010.htm.
a
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24 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
these on the already complex task of assessing damages through the NRDA
process, Congress sought external input on the process from the National
Academy of Sciences (NAS). Funding was provided to the National Research
Council (the operating arm of the NAS) through the National Oceanic and
Atmospheric Administration (NOAA) to study approaches to evaluating the
impact of the DWH spill related to the ecosystem services of the GoM.
Specifically, the NAS was asked to address the questions listed in Box I.2.
It is important to note that the Statement of Task described above does
not include a review of the ongoing damage assessment process. With
respect to the DWH spill, such a review would be premature and inap-
propriate at present. It does, however, recognize (without stating explicitly)
the challenges that the DWH spill will place on the ongoing NRDA process
and seeks input from the NAS on new approaches that may aid and comple-
ment the NRDA process. In particular the Statement of Task focuses on an
“ecosystem services” approach (NRC, 2005a) to assessing impact and to
estimating the value of losses due to injury. Such an approach focuses not
only on the restoration of damaged resources (as per NRDA practice) but
also on establishing and maintaining the usefulness of those resources to
the public. It is this broader view that may be particularly appropriate to an
event of the magnitude, duration, depth, and complexity of the DWH spill.
A committee comprising 16 members (see Appendix A) representing a
broad range of relevant disciplines (benthic ecology, biochemistry, biologi-
cal oceanography, chemistry, ecology, economics, environmental engineer-
ing, environmental law, fisheries, geology, geophysics, human dimensions of
natural resource management, microbiology, and veterinary medicine) was
formed in January 2011 and held its first meeting January 24-25, 2011. To
assist the federal agencies in their preparation of the NRDA, the committee
was charged with providing an interim report approximately six months
following the first meeting that addresses questions 1 through 3 of the State-
ment of Task. A final report, encompassing the interim report and including
questions 4 through 8, is to be delivered after 24 months.
The generic questions 1 through 3 of the Statement of Task that are the
focus of this interim report deal with best approaches to the difficult ques-
tion of estimating the impact on ecosystem services of a human-caused
disaster like the DWH spill. They seek to provide guidance on methods for
identifying critical ecosystem services, for understanding the relevant spatial
and temporal scales that need to be studied, and for establishing the base-
lines critical in determining the “injuries” caused by the incident. The third
question focuses on the specific problem of assigning value to the impacted
ecosystem services. These questions are best addressed with reference to
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25
INTRODUCTION
BOX I.2 STATEMENT OF TASK
1. What methods are available for identifying and quantifying various
ecosystem services? What are the spatial and temporal scales condu-
cive to research that provide meaningful information for the public
and decision makers?
2. What methods and types of information can be used to approximate
baselines (but for the spill) for distinguishing effects on ecosystem
services specific to the spill?
3. What kinds of valuation methods are appropriate for measuring eco-
system services over time with regard to recovery under the follow-
ing approaches: natural processes, mitigation, and restoration efforts?
What baseline measures are available that would provide benchmarks
for recovery and restoration efforts?
4. What ecosystem services (provisioning, supporting, regulating, and
cultural services) were provided in the GoM LME prior to the oil spill?
How do these differ among the subregions of the GoM?
5. In general terms, how did the spill affect each of these services, and
what is known about potential long-term impacts given the other
stresses, such as coastal wetland loss, on the Gulf ecosystem?
6. How do spill response technologies (e.g., dispersant use, coastal berm
construction, absorbent booms, in situ burning) affect ecosystem ser-
vices, taking into account the relative effectiveness of these techniques
in removing or reducing the impacts of spilled oil?
7. In light of the multiple stresses on the GoM ecosystem, what practical
approaches can managers take to restore and increase the resiliency
of ecosystem services to future events such as the DWH spill? How can
the increase in ecosystem resiliency be measured?
8. What long-term research activities and observational systems are
needed to understand, monitor, and value trends and variations in
ecosystem services and to allow the calculation of indices to compare
with benchmark levels as recovery goals for ecosystem services in the
GoM?
ecosystem services provided by the GoM LME and thus we will frame our
responses within that context. We also acknowledge that there is a number
of human health issues associated with the DWH event, but we will not
address them, as they are specifically the subject of an Institute of Medicine
(IOM) 2010 letter report: Research Priorities for Assessing Health Effects from
the Gulf of Mexico Oil Spill (Institute of Medicine, 2010).
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26 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
The lexicon of natural resource damage assessment uses many words
that may seem familiar but have very specific (and sometimes multiple) defi-
nitions within the context of the process. Terms that will be used throughout
the report are defined below. Chapter 1 outlines the geographic, oceano-
graphic, and ecological context of the GoM LME. Chapter 2 explores the
typical practice of damage assessment and introduces the ecosystem services
approach to damage assessment. Chapter 3 describes methodologies for
establishing baseline information for ecosystem services and, where pos-
sible, discusses existing baseline data. Finally, Chapter 4 takes a detailed
look at the ecosystem services approach including methods to identify and
quantify ecosystem services and, taking this one step further, looks at the
most appropriate methodologies for assessing the value of key ecosystem
services. Each of these issues, as well as the additional questions presented
in the Statement of Task, will be addressed in more detail in the final report.
DEFINITIONS OF TERMS
Ecosystem: A complex, interactive system consisting of all organisms in a
particular area, the physical components of the environment within which
the organisms interact, physical features including hydrology, temperature,
geology, air quality, and others, and the flow and transformation of en-
ergy and matter between organisms, and organisms and the environment.
Eugene Odum defined an ecosystem as “Any unit that includes all of the
organisms (i.e., the ‘community’) in a given area interacting with the physi-
cal environment so that a flow of energy leads to clearly defined trophic
structure, biotic diversity, and material cycles (i.e., exchange of materials
between living and nonliving parts) within the system” (Odum and Barrett,
2005). Increasingly, it is evident that human beings are a critical component
of ecosystems; consideration of ecosystems must include the influence of
human social structure on the ecosystem, as well as the influences of the
ecosystem on human society.
Large marine ecosystem: In order to define specific large geographic areas
for resource management, river basins, estuaries, and coastal shelf areas
have been subdivided into “large marine ecosystems” (LMEs). LMEs are
defined by unique hydrography, bathymetry, and productivity (Griffis and
Kimball, 1996). They may cross international borders, providing unique
opportunities and challenges for successful management.
The Gulf of Mexico is recognized as a distinct Large Marine Ecosystem.
The GoM LME is one of the most biologically productive in the world. It
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27
INTRODUCTION
crosses boundaries between the United States, Cuba, and Mexico and pro-
vides an opportunity for transnational management of important natural and
cultural resources. Habitats within the GoM LME include coastal wetlands,
salt marshes, mangroves, sandy beaches, coastal shelf marine ecosystems,
and deep-sea marine ecosystems. Each habitat provides distinct services that
need to be accounted for in any valuation of the impacts of the Deepwater
Horizon oil spill. The geographic, oceanographic, and ecological contexts
of the GoM LME are discussed in Chapter 1.
Ecosystem structure: Ecosystem structure refers to both the (species) com-
position of the ecosystem (i.e., its various organisms) and the physical
and biological organization defining how those parts are organized (NRC,
2005a). The Gulf of Mexico has recently been estimated to contain in excess
of 15,000 species exclusive of microbes (Felder and Camp, 2010).
Ecosystem function: A process that takes place in an ecosystem as a result
of the interactions of plants, animals, microorganisms, and their environ-
ment. Primary production, most notably the generation of plant material, is
an example of an ecosystem function (NRC, 2005a). All recognized coastal
and oceanic ecosystem functions operate in the Gulf of Mexico.
Ecosystem service: There is a rich and evolving literature on ecosystem ser-
vices with a variety of definitions (e.g., Westman, 1977; Ehrlich and Mooney,
1983; de Groot, 1987; Barbier, 1994; Costanza et al., 1997; Daily, 1997;
Wilson and Carpenter, 1999; de Groot et al., 2002, Millennium Ecosystem
Assessment, 2005; NRC, 2005a; EPA, 2009; TEEB, 2009). The common
thread through all of these definitions is a relationship between ecosystems
and the value humans derive from them. In 2000, the United Nations com-
missioned the Millennium Ecosystem Assessment (MA) to summarize the
current status and future conditions of biodiversity and ecosystems and
determine the consequences of ecosystem change for human well-being.
The MA defines ecosystem services as “the benefits provided by ecosystems
to humans which contribute to making human life both possible and worth
living.” Moreover, the MA defined explicit categories of ecosystem services
including provisioning, regulating, cultural, and supporting services. These
service categories are now widely accepted. In order to apply the MA
definition to the GoM, the definition needs to make explicit the distinction
between the different ecosystems present in the GoM LME and the goods
and services provided by each.
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28 APPROACHES FOR ECOSYSTEM SERVICES VALUATION FOR THE GULF OF MEXICO
Value: In this report we use the term value in the way that economists tend
to define it. The value of an item is measured by its contribution to human
well-being. A measure of the value of a good or service to an individual
can be obtained by observing what the individual is willing to give up in
exchange for an increase in the good or service. Economists typically attempt
to measure benefits in monetary terms by seeing how much an individual
would be willing to pay to obtain more of a good or service. Alternatively
value can be measured by, what an individual would be willing to accept
for less of the good or service. For ecosystem services that are provided to
the public at large, the value of a change in the ecosystem service would
be found by summing up the estimated values across all individuals affected
by a change in the provision of the service. This aggregated value would
then represent an overall societal value that occurs because of a change in
the ecosystem.
Economists have several methods that may be used to determine the
value of particular ecosystem services. These methods are generally divided
into market valuation methods that are based on market prices, and non-
market values in which proxies for prices are developed either from ob-
served behavior (revealed preference methods) or from responses to survey
questions (stated preference methods). Some ecosystem services contribute
to marketed commodities (e.g., commercial fisheries) but most ecosystem
services do not. It tends to be more difficult to place an economic value
on a service where there is no actively traded good or service in a market.
Though even among non-marketed ecosystem services there is a range of
difficulty, with those that affect recreation being more amenable to valuation
than the existence value of a species or spiritual or aesthetic values. This
committee has been tasked with describing the strengths and weaknesses of
various valuation methods rather than placing a specific monetary value or
some other quantitative estimate of value on the impact of the DWH spill
on ecosystem services. Approaches to valuation of ecosystem services will
be discussed in Chapter 4.
Baseline: The condition of the natural resources and services that would
have existed had the incident not occurred.5 Within the context of the
DWH spill and a system like the GoM that has numerous factors impacting
ecosystem health, the concept is to establish conditions “but for the spill.”
Approaches for establishing baselines for various ecosystem services and
baseline data sources (if available) for the GoM LME will be presented in
See http://www.dem.ri.gov/topics/erp/app2_3.pdf.
5
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29
INTRODUCTION
Chapter 3.
Resilience: Narrowly defined, resilience is the ability of an ecosystem to
recover following a perturbation. As described in the NRC report Increas-
ing Capacity for Stewardship of Oceans and Coasts (2008b), “Resilience
thinking is one new approach to addressing the decline in the capacity of
communities, ecosystems, and landscapes to provide essential services. The
intent is to recognize the complexity and variability of ecosystems, including
the human component, and to build nature-human systems that can adapt
to incorporate new knowledge or adjust to changing conditions.”
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